Bone remodels in response to load. That idea, usually called the mechanostat theory, is well established, and it is the reason weight-bearing and resistance work show up in almost every bone health guideline.
The real question for a Pilates studio is how you deliver meaningful load without breaking the person who came to you because everything else hurt.
Our answer is a progression. Reformer, Tower, and Chair work to establish control. Konnector-loaded standing work to build tolerance. Then coached free-weight strength in our small group circuit classes.
Bone changes slowly and the only way to measure them is a DEXA scan ordered by your doctor, so plan on this being a long-term habit. If you have osteoporosis or a recent fracture, start with a physical therapy assessment so we know which movements to adapt before you join a class.